The invention relates to silicate glasses. More particularly, the invention relates to silicate glasses in which the content of non-bridging oxygen atoms in the glass is minimized. Even more particularly, the invention relates to such silicate glasses that are scratch resistant and less susceptible to edge chipping.
Glass has the drawback of being brittle. Brittleness is generally is understood to be the ratio of the hardness divided of the glass to its fracture toughness. Such brittleness leads to breakage, defects, and edge chipping, all of which are particularly problematic in applications such as cover plates for mobile electronic devices, touch screens, watch crystals, solar concentrators, windows, screens, containers, and the like. Glass compositions having higher toughness are less brittle, resist crack propagation, and are less prone to other types of damage, such as edge chipping. Softer (i.e., less hard) glasses are less brittle, but are less scratch resistant.